Mechanical switches including replays, contactors and the like are widely used in circuits. Since some mechanical switches (e.g. a relay) have advantages of being small in size and enabling electrical isolation, the relay can be used in a battery management system to control charging and discharging of a battery. At the moment the relay is turned on, an inrush current may be generated in the circuit to cause contact ablation; or at the moment the relay is turned off, an electric arc may be generated to cause contact ablation. The inrush current at the moment the relay is turned on and the electric arc at the moment the relay is turned off are unavoidable. The contact ablation in the relay may lead to an increased contact resistance of the relay, resulting in an increased amount of heat produced at the use of the relay and a reduced serve life of the relay.